Automatically adjustable choke for shotguns



Feb. 28, 1961 A. Y. GRAHN 2,972,829

AUTOMATICALLY ADJUSTABLE CHOKE FOR SHOTGUNS Filed March 27, 1958 ATTORNEYS "l4 and'the threads at the rear end of the member. the region of the flange 14 the cylindrical member 12 is United States Patent AUTOMATICALLY ADJUSTABLE CHOKE FOR SHOTGUNS ArnenY. Grahn, Hartford, Conn., assignor to The Poly Choke Company, Incorporated, East Hartford, Conn., a corporation of Connecticut ,This invention relates to a choke mechanism for firearms, and especially shotguns,, and relates more particularly to an automatically adjustable choke mechanism in which the adjustment of the choke is effected by the firing or discharge of the gun. The choke is also manually adjustable and is of the type employing an inexpansible choke tube. The choke tube is movable lengthwise of the gun barrel and the choking action is obtained by varying the distance of the tube from the muzzle of the gun. In other words, the choking action is obtained by, in effect, lengthening the gun barrel.

One object of the invention is to provide an improved automatically adjustable choke mechanism which very effectively chokes a shotgun and which is very reliable in operation. V

. Another object of the invention is to provide an automatically adjustable choke mechanism such as characterized above, in which a choke tube of new and improved form is employed.

Another object of the invention is to provide a choke mechanism having improved means for manually locking the choke tube in an adjusted positionthereof so that when the .gnn-is subsequently discharged the tube remains stationary and no further choking action is obtained on the next-following shot. r In the drawing: 1 H

Fig. .1 is a side elevational view of the muzzle of a gun barrel having a choke embodying the invention ap plied thereto; 4

Fig. 2-is an enlarged sectional view taken on line 22 of Fig. l: and illustrating the choke tube in its rearmost P s 1 1 Fig. 3 is a view similar to Fig. 2 and illustrating the choke tube in a forward choking position; I Fig.4 is a sectional view taken on line 4-4 of Fig. 2 and illustrating one angular position of a split ring employed in the choke mechanism;

, Fig. 5 is a view generally similar to Fig. 4 and illustrating the split ring in another angular position thereof; and Fig. 6 is a further enlarged fragmentary view, the view being a sectional view taken lengthwise of the choke tube and illustrating the split ring and some of the parts of the choke mechanism associated therewith.

Toillustrate the presently preferred embodiment of the invention, there is shown in the drawing the muzzle of a gun barrel 10 having secured thereto by brazing or equivalent means an adapter 11. The forward end portion of the adapter 11 is provided with external screw threads for mounting a hollow cylindrical member 12 having internal threads at the rear end thereof so that it may be threadedly secured to'the adapter.

As shown in Fig. 2, the internal diameter of the cylindrical member 12 is somewhat greater than the bore 13 of the gun barrel and has at its forward end an inwardly extending circumferential flange 14, the bore of the member 12 being smooth or uninterrupted between the flange In ice . 2 provided with an external circumferential groove 15. An inexpansible choke member 18 of tubular form is slidably mounted within the member 12 and has at its rear end a circumferential outwardly extending flange 19 to impinge the flange 14 and thereby limit outward movement of the member 18. In the rear position of the member 18 the flange 19 is spaced rearwardly of the flange 14, as shown in Fig. 2, while in the forward position of the member, shown in Fig. 3, the flanges are in abutting relationship.

An outer cylindrical or sleeve member 20 embraces the hollow cylindrical member 12, the member 20 having a side-wall structure providing clearance with the sidewall structure of the member 12. As shown in Fig. 2, the sleeve member 20 is shorter than the cylindrical member 12 and at its outer end is provided with an inwardly extending circumferential flange 21, the flange being threadedly secured to external threads formed at the forward end of the choke member 18. ,Thus it will be understood that the choke member 18 is, in effect, integral with the outer sleeve member 20 and in its movements carries the member 20 with it. Hence the members 18 and 20, when secured together, may be referred to as the choke tube. A locking mechanism (the details of which will appear hereinafter) is provided so that the choke tube may be locked'manually in its rear position. The sleeve 20 may have an externally knurled portion 22 so that it' may be readily grasped for manipulation. The member 20, at its forward end, is provided with an internal circumferential groove 23 which, in the position of the choke tube shown in Fig. 2, opposes the groove 15 and provides forward and rear annular shoulders 16 and 17, respectively. A split ring 24 is provided to extend into and be carried by one of the grooves while bearing against the bottom of the other groove when the choke tube is in its rear position. In the present instance the ring 24 is carried by the groove 15 and bears against the bottom of the groove 23 when the choke tube is in the rear position of Fig. 2. In the illustrated form the groove 15 and the split ring 24 are so dimensioned that when the choke tube is unlocked in its rear position and suificient forward thrust is exerted on the choke tube, the split ring may be compressed in the groove 15 to permit the sleeve member 20 to slide over the split ring 24 against the frictional drag of the latter. As shown in Fig. 6, the split ring is of a depth less than the groove 23 and is tapered to cooperate with the rear shoulder 17 of the groove.

Turning now to the construction of the bore of the choke member 18, it will be noted that, as shown in Fig. 2, an intermediateportion of the bore is defined by a cylindrical wall portion 26. Adjoining and forwardly of thewall portion 26 the bore is provided with an outwardly flared wall portion 27 of considerably less length than the portion 26 and extending to the forward extremity of the choke member 18. Adjoining and rearwardly of the wall portion 26 the bore is provided with an outwardly flared wall portion 28 extending to the rear extremity of the member18 to restrict or collect the shot delivered from the muzzle of the gun barrel. As shown in Fig. 2, the surface providing the flared wall portion 28 is not truly conical in longitudinal section but instead may be considered as arcuate. It is somewhat convex in form. Due to the provision of the convex surface 28 of the member 18, the shot, when it is delivered from the muzzle of the gun barrel, strikes the member 18 with less impact than would be the case if this flared portion of the member 18 were truly conical.

As shown in Fig. 2, the tubular member 18 in its rearmost position is spaced forwardly of the muzzle of the gun barrel a distance which in actual practice may ap proximate of an inch or more, the arrangement being such that the shot leaving the gun barrel may expand to some extent before entering the tubular member 18. Rearward movement of the choke tube from this position is prevented by engagement of the flange 21 of the tube with the forward end of the .fixed member 12. shown in the last-mentioned view, the flared portion 28 of the bore at its widest .point is of somewhat greater diameter than the diameter of the gun barrel 13. The flared portion 28 of the choke member 18 serves to collect the shot from the gun barrel and direct it to the wall portion 26 of the member 18, the last-named portion of the member '18 being of approximately the same diameter as the gun barrel. When the shot leaves the wall portion 26 itimay expand to some extent in the wall portion 27' of the choke member before leaving the choke mechanism.

The automatic operation of the choke mechanism is as follows. When'the choke tube is in the rear position of Fig. 2 and is unlocked, a subsequent single discharge of the gun efiects compression of the split ring by the choke tube and outward movement of the latter against the frictional resistance of the split ring, the tube being moved to the extreme position of Fig. 3. .This lengthwise movement of the choke tube is effected by the impact of the charge on the wall defining the shot-collection portion of the choke member 18. During this movement the choke tube tends to remain in the same angular position to the fixed cylindrical member. In other words, during this movement the choke tube does not tend to rotate. The choke tube may also be manipulated to move it from the rear position of Fig. 2 to the forwardposltion of Fig. 3. As shown in the last-mentioned view, the flange 19of the choke member is engaged with the flange 14 of the hollow cylindrical memher to prevent runner forwardmovement of the choke tuoe. Therefore, on the nextfollowing shot the choke tube remains stationary. In this extended position of the choke tube the gun barrel is, in effect, lengthened to provide a closer shot pattern.

Turning now to the details of the lock for'holding the choke tube'in its rear position, there is shown in Figs. 3 through 5 a lock pin 30,-for cooperationwith the split ring 24. The pin 30 extends across'the bottom of the groove 15 in the cylindrical member '12 andis held in fixed position in the from and rear walls of the groove, the pin extending through the front end of the member 12. As shown in Fig 4, the ends of the split ring 24 are spaced a sufficient distance apart that-the pin 30 may be interposed between the ends with clearance. As shown in the last-mentioned view, the end '3'1of the ring is blunt. The diameter of the lock pin 30 is such that the blunt end 31 of thering will not pass between it and the bottom. of the groove 23. However, the other end of the ring is tapered, as at 32, and may be wedged between the lock pin 30 and the bottom of the groove 23 when the choke tube is in the rear position thereof and manipulated toro'tate the same from the position of Fig. 4 to the position of Fig. 5. It will be understood that the split ring bears against the sleeve member '20 of the choke tube so as to be rotatable with it when it is in the rear position. However, when the ring does 'not extend into the groove 23 the ring is compressed by the sleeve member 20 so such an extent that it will not overlap the pin 30. I

' From the foregoing it will be understood that the "choke tube may be locked in its rear position by manipinlating the choke tube to wedge the tapered end of the ring between the'pi'n and the sleeve member 20. It will be undet'stoodthat' lockingofthe choke tube is accomplishedby interposing the, n'ngbetween the pin 30 and the sleeve member 20' so that'it cannot be compressed fin the groove 15 to clear the groove 23 when the gun is discharged. When the ring is in the last-mentioned position, the choke tube is effectively held against axial the gun sat-es.

V out of order.

In accordance with the foregoing disclosure that: I provided an improved choke mechanism adjustable both automatically and manually and including a choke tube of the inexpansible type. One advantage of the choke mechanism resides in the simple and yet efiective lock mechanism for holding the choke tube in an adjusted positionso that it is eifectively locked against axial movement when the gun is discharged. Another advantage of the choke mechanism resides in the construction of the choke tube. The choke mechanism is constructcd of few and rugged parts and will not easily get It is also very eflicient and satisfactory in operation.

While only one form of the choke mechanism has been illustrated in the drawing and described above, it will be apparent to those versed in the art that the choke mechanism is susceptible of various modifications and changes in details without departing from the principles of the invention and the scope of the claims.

What I claim is: V V

1. A choke mechanism comprising'a hollow cylindrical member extending outwardly from the muzzle of a gun barrel in fixed relation thereto, a choke tube having a charge-choking tubular part extending into said member in slidable relation thereto, for forward propulsion by impact thereon of 'acharge fired from the gun, said tubular part being adjustable lengthwise of said member, said choke tube also comprising a sleeve part embracing said cylindrical member and fixed to said tubular part 'for'movement'withthe latter, frictional means restraining lengthwise movement of said tubular part, said means comprising a contractable split ring interposed between one of said parts and said cylindrical member, and means operable by manipulation and cooperating was said split ring for locking the tubular part in an adjusted position, the last-named means comprising a wedge member extensible into wedging relation with the contrsetnble split ring. I

2. A ehokemechanism comprising a hollow cylindrical member extending outwardly from the muzzle o! a gun barrel in fixed relation thereto, achoke tube having a charge-choking tubular part extending into said meniber in slidable and rotatable relation thereto, for for ward propulsion by impact thereon of a charge fired from the gun, said tubular part being adjustable lengthwise of said member, said choke tube alsocomprisin'g a sleeve part embracing said cylindrical member and fixed to said tubular part for movement with the latter, a contractable split ringrestraining lengthwise movemerl of said "tubular part and interposed between the sleeve part and said cylindrical member, and means operabb by manipulation and cooperating with said split ring for locking" the tubular part in an adjusted position, the last-named means comprising a wedge member carried by said cylindrical member and cooperating with the friction ring to wedge the latter against the sleeve part on angular adjustment of the last-mentioned part.

3. A choke mechanism comprising a hollow cylindrical member extending outwardly from the muzzle of a gun barrel in fixed relation thereto, a choke tube having a charge-choking tubular part extending into said member in slidable and rotatable relation thereto, for forward propulsion by impact thereon of a charge tired from the gun, said. tublar part being adjustable lengthwise of said member, the choke tube also comprising a sleeve part embracing said cylindrical member and fixed to said tubular part for movement therewith, one of said parts and said member having circumferential grooves termed therein which'in one adjusted position of the tubutar part one another, frictional means for restraining lengthwise movement of said tubular part, said eomprising'acontraetable split ring carried in one of said grooves and extending into ,the other groove when the tubularpart is insaidadjus'ted position, and means operable bymanipumtoa and rotation of the sleeve part for locking the tubular part in said adjusted position, the last-named means comprising a pin carried in said one of the grooves and extending thereacross in fixed relation, the pin being movable relatively to the ring to wedge the ring in said other groove.

4. A choke mechanism comprising a hollow cylindrical member extending outwardly from the muzzle of a gun barrel in fixed relation thereto, a choke tube having a charge-choking tubular part extending into said member in slidable relation thereto, for forward propulsion by impact thereon of a charge fired from the gun, said tubular part being adjustable lengthwise of said member, frictional means for restraining lengthwise movement of said tubular part comprising a contractable split ring, and means operable by manipulation and cooperating with the first-named means for locking the tubular part in an adjusted position, the last-named means comprising a wedge member extensible into wedging relation with the ring.

5. A choke mechanism comprising a hollow cylindrical member extending outwardly from the muzzle end of a gun barrel in fixed relation thereto, a choke tube having a charge-choking tubular part extending into said member in slidable and rotatable relation thereto, for forward propulsion by impact thereon of a charge fired from the gun, said tubular part being adjustable lengthwise of said member, the choke tube also comprising a sleeve part embracing said cylindrical member and fixed to the tubular part for movement therewith, said sleeve part having at the forward end portion an internal circumferential groove which in one adjusted position of the sleeve part opposes an external circumferential groove formed in the cylindrical member, a friction ring carried in the groove in the cylindrical member and extending into the groove in the sleeve part when the latter is in said adjusted position, and a pin carried in the groove in the cylindical member and extending thereacross in fixed relation, the pin being movable relatively to the ring to extend under the latter and wedge the ring in the groove of said sleeve part when the sleeve part is angularly adjusted.

6. A choke mechanism comprising a hollow cylindrical member extending outwardly from the muzzle of a gun barrel in fixed relation thereo, a choke tube having a chargechoking tubular part extending into said member in slidable and rotatable relation thereto, for forward propulsion by impact thereon of a charge fired from the gun, said choke tube being adjustable lengthwise of said member, frictional means for slowing lengthwise movement of the choke tube upon impact of a charge on said tube part and including an axially fixed friction member movable in a plane transversely of the choke tube and engageable with the tube and means operable by manual rotation of said choke tube and cooperating with said friction member for locking the choke tube in one position so that the choke tube is positively held against movement on discharge of the gun, the last-named means comprising a locking recess formed in the choke tube and an actuator member for engagement with the friction member to lock the latter in the locking recess in the choke tube.

7. A choke mechanism as defined in claim 6, wherein the friction member comprises an expansible and contractable ring and wherein the locking recess is formed in a slidable part of the choke tube which embraces said hollow cylindrical member.

8. A choke mechanism comprising a hollow cylindrical element extending outwardly from the muzzle of a gun barrel in fixed relation thereto, a choke tube element having a charge-choking tubular part extending into said cylindrical element in slidable relation thereto for forward propulsion by impact thereon of a charge fired from the gun, said tubular part being adjustable lengthwise of said cylindrical element, means for positively locking the choke tube element in one position and including a member disposed intermediate a wall portion of said cylindrical element and a wall portion of said choke tube element, said member being movable relatively to both elements and comprising an expansible and contractable ring, one of said elements having a locking recess formed therein which in said one position of the tube is opposite the locking member, and means to move said locking member into the locking recess, the locking member when unlocked acting frictionally to slow forward propulsion of the tube by impact thereon of a charge from the gun.

References Cited in the file of this patent UNITED STATES PATENTS 1,773,260 Cutts Aug. 19, 1930 2,428,232 Limon Sep. 30, 1947 2,453,121 Cutts Nov. 9, 1948 2,484,988 Finlay Oct. 18, 1949 2,676,429 Gotterson Apr. 27, 1954 2,888,769 Grahn June 2, 1959 2,894,349 Hare July 14, 1959 

